A speed-reducing gear mechanism with input and output arranged coaxially in line; common types are planetary, parallel shaft and harmonic. Reduction ratio 3:1–100:1, output torque 5–500 Nm. Used in CNC feed axes, automated machines, conveyors and robot joints.
A linear gearbox (in-line reducer) is a reducer whose input and output shafts are coaxial. Compared with a right-angle gearbox (90°), it is long and slim and easy to integrate into a machine, with high transmission efficiency (90–97%) and low backlash. Common types include planetary, parallel shaft and harmonic reducers.
This series covers in-line gearbox mechanical drive components. A JIAHON affiliated company supplies customers throughout Taiwan.
Specifications
| Item | Range |
|---|---|
| Type | Planetary / parallel shaft / harmonic drive |
| Housing | Cast iron / aluminum alloy (small) / stainless steel (cleanroom / food and medical) |
| Reduction ratio | Single stage 3:1–10:1 (planetary); two stage 9:1–100:1; three stage up to 1000:1 (more noise and efficiency loss) |
| Output torque | 5–500 Nm (typical) |
| Input speed | 500–6000 rpm (depends on the motor) |
| Efficiency | Planetary single stage 95–97% / two stage 90–94% / parallel shaft 92–95% / harmonic 70–90% |
| Backlash (precision grade) | Standard < 30 arcmin / precision < 5 arcmin / ultra-precision < 1 arcmin (harmonic) |
| Operating temperature | −10 °C to +90 °C (standard) |
| Lubrication | Lifetime sealed (small) / serviceable with oil (medium and large, ISO VG 220–320 gear oil) |
| Motor mounting | Standard IEC / NEMA / custom flanges; for stepper, servo and AC motors |
Note: these are typical ranges; actual type, ratio and torque depend on the machine and the maker’s catalog. Model on this page: M9GA180B; other types and ratios available on request.
Applications
Four typical applications:
- CNC feed mechanisms: X/Y/Z feed axes with servo motor + planetary gearbox, combined with a ball screw for precise linear positioning. Ratio 5:1–10:1, precision-grade backlash.
- SMT placement machine axes: high-speed X/Y pick-and-place and Z-axis pressing. High torque density and low backlash are needed to maintain placement accuracy; planetary gearboxes are commonly used.
- Robot joints: joint drives on 6-axis / 4-axis robots, mostly with harmonic reducers (backlash < 1 arcmin, flat design).
- Conveyors / belt drives: packaging lines, SMT board conveyors and semiconductor wafer transfer. AC motor + parallel shaft gearbox, ratio 10:1–100:1.
Selection guide
| Use | Recommended type | Ratio | Backlash |
|---|---|---|---|
| High-precision CNC positioning | Planetary (precision grade) | 5:1–10:1 | < 5 arcmin |
| SMT placement machine | Planetary (precision / ultra-precision) | 3:1–10:1 | < 3 arcmin |
| Robot joint | Harmonic | 50:1–100:1 | < 1 arcmin |
| General conveyor | Parallel shaft | 10:1–100:1 | < 30 arcmin |
| Heavy machinery | Parallel shaft / worm | 50:1–300:1 | Not critical |
Note: this table is a general reference; type, ratio and accuracy depend on the machine’s accuracy requirement, torque demand and the maker’s catalog.
The 3 main types compared
| Type | Construction | Efficiency | Backlash | Relative cost | Typical use |
|---|---|---|---|---|---|
| Planetary | Sun + planet gears + ring gear | 95–97% | 3–30 arcmin | Medium–high | CNC, SMT, servo |
| Harmonic | Circular spline + flexspline + wave generator | 70–90% | < 1 arcmin | High | Robots, semiconductor |
| Parallel shaft | Conventional gear mesh | 92–95% | — | Low | Conveyors, AC motors |
Reduction ratio and torque calculation
Ratio i = input speed ÷ output speed; output torque = input torque × ratio × efficiency.
Example: motor 3000 rpm / 1 Nm, target output 100 rpm / 50 Nm. Ratio = 30:1, output torque = 1 × 30 × 0.95 = 28.5 Nm (short of 50 Nm). Switching to 50:1 gives 47.5 Nm (still short), and the output speed drops to 3000 ÷ 50 = 60 rpm, missing 100 rpm. A power check shows why: the load needs 50 Nm × 100 rpm ≈ 524 W, while this motor delivers only 1 Nm × 3000 rpm ≈ 314 W; a gearbox only trades speed for torque and cannot add power (even at 100% efficiency it is only 30 Nm). The correct fix is to keep 30:1 and upgrade the motor to a rated torque of about 1.75 Nm (50 ÷ 30 ÷ 0.95) and about 550 W or more.
Common ratios: 3:1, 5:1, 10:1, 15:1, 20:1, 30:1, 50:1, 100:1. A single planetary stage covers 3:1–10:1; larger ratios need 2–3 stages (cost multiplies).
Maintenance and troubleshooting
- Lifetime sealed vs serviceable: small planetary / harmonic units are mostly lifetime sealed and replaced as a whole when they fail; medium and large parallel shaft / worm units need ISO VG 220–320 gear oil changed every 2000–5000 hours (typical experience; follow the maker’s specification and operating conditions).
- Warning signs: housing hotter than 85 °C, abnormal noise, oil turning dark or foaming, oil leaking at the shaft (typical experience). Stop and inspect if any of these appear.
- Do not overload: running above rated torque for long periods accelerates gear wear, backlash gradually increases and teeth eventually break. When the load increases, upsize the gearbox accordingly.
Request a quote
Need a quote or want to confirm specifications? Send us the type, ratio, torque and motor flange. Request a quote →